Abstract des Autors

Die im Gegensatz zu den Unterschenkelfrakturen in den letzten Jahren nicht ruecklaeufige Zahl der Knieverletzungen beim Skifahren sowie die relative Zunahme der schweren Knieverletzungen und der isolierten Kreuzbandruptur veranlassten uns, eine umfassende Ursachenforschung auf diesem Gebiet durchzufuehren. Zur Analyse der mit den Knieverletzungen ursaechlich in Verbindung gebrachten Bewegungs- und Belastungsmuster war es notwendig, ein neuartiges Messverfahren zu entwickeln. Durch Kombination und Synchronisation von Bewegungsanalyse, Druckverteilungsmessung und Kraftmessung wurde es moeglich, die Vor/Rueckbewegung im Skischuh im Labor und mittels Telemetrie auch auf der Piste genauer zu analysieren. Dieser Beitrag (Teil I) liefert die grundlegenden Informationen ueber Methodik und die Notwendigkeit zu solch aufwendigen Verfahren. Verf.-Referat (gekuerzt)

Abstract des Autors

In contrast to the drop in the incidence of fractures of the lower leg, or tibia, that has been observed in recent years, the incidence of knee injuries has not decreased in skiing and there has been a relative increase in the frequency of severe knee lesions and of the isolated rupture of the cruciate ligament, prompting us to conduct a comprehensive study of the causes of these phenomena. It was found necessary to develop a innovative method of measurement to analyse the patterns of movement and stress to which the knee injuries were attributed. By combining and synchronising movement analysis, measurement of pressure distribution and measurement of force it became possible to perform a detailed analysis of the forward/backward movement in the ski boot in the laboratory and also on the course by telemetry (part 1). The first two studies were devoted to the forward lean in the ski boot (part 2). Basing on movement analysis and simultaneous determination of pressure distribution along the lower leg, the influence of different ski boot models on the Vorlage, or forward lean, movement of beginners and very experienced skiers was studied. An important result of the laboratory experiment was that whereas a ski boot can be moved without difficulty into a strong forward lean position of the skier by an experienced sportsman, a beginner can only assume a forward lean with 20 % less inclination (this being a significant difference). In other words: the range of the freedom of movement in such a boot is markedly limited. The assumption that in ski amateurs such a ski boot would promote skiing in backward lean position, was confirmed by studies on the course (part 3). The pupils became definitely less adept at learning if they were required to wear a stiff ski boot; analysis of movement showed that the forward lean angles were clearly smaller and that the skiers adopted a skiing style in backward lean position that exercised an undue strain on the knees. The other two studies, therefore, focussed mainly on the backward movement in the ski boot. Specifically, the fixed rear spoilers of the modern ski boots are accused of contributing to the rupture of the anterior cruciate ligament if the skier lands on the tail ends of the skis after a jump or fall in backward lean position (‘big bump, flat landing’ syndrome). To measure the horizontal force at the rear spoiler, a new experimental laboratory setup was devised to conduct a movement analysis and at the same time to determine the force/time graph when falling backward. To quantify the influence of the rear spoiler,a special ski boot was constructed allowing the rear spoiler to give way in the backward lean position. This made it possible to compare for the same boot model a fixed rear spoiler with a spoiler of variable rigidity in backward lean position. The results obtained in the laboratory showed most clearly that even a medium rear spoiler resistance will reduce the peak force values by a factor of 5.5. The acceleration at the knee joint level, calculated by means of the movement analysis, is significantly higher in case of a rigid spoiler; this supports the results found by us. Moreover, it was also possible to quantify the individual positions during the backward movement. The subsequent studies conducted on the course confirmed these results, showing that normal skiing can be performed in such a boot without limitations or difficulties. A reduction of the peak force values by the factor 8 was seen in a ski jump with comparable angles. Today's ski boots promote skiing in backward lean position by their construction. A rigid rear spoiler will considerably enhance the risk of a lesion of the cruciate ligament when falling backwards or when landing on the tail ends of the skis after a jump, compared with a model with a rear spoiler that will give way, or with the previously employed leather ski boots that gave way in backward direction. The combined measurement method made it possible for the first time to analyse and record the total course of the movement in the ski boot and the ensuing forces during forward/backward movement. The complex problem of skiing in backward lean position was fully understood only by considering the results of pressure distribution and movement analysis in forward movement and of measuring the force FH as well as by considering the movement analysis data during backward movement, as a whole. In consideration of these facts it is concluded that the principle of safety binding which is meanwhile selfunderstood in skiing (the skiers being equipped without exception with a safety binding device) must definitely apply in future in equal measure also to the ski boot. The backward-releasing bindings, which can often produce dangerously inappropriate releases if a strong force acts on them for a short while, and which were therefore only very reluctantly if at all accepted by skiers for whom skiing is a major sport, could thus be complemented by a safety system in the boots. In all probability this would be a contributing factor to reducing the high incidence of knee injuries in skiing.